Conventionally, a relief valve is installed in a refrigeration cycle device mounted on a vehicle as a safety apparatus provided for an excess increase in pressure of a refrigerant. The relief valve has a role to release the pressure of the refrigerant to outside the refrigeration cycle device by opening when the pressure of the refrigerant becomes higher than or equal to a predetermined pressure.
A reason of the excess increase of a refrigerant pressure is that, for example, an atmospheric temperature around the refrigeration cycle device increases to a high temperature when the refrigeration cycle device is stopped (i.e., when a compressor is stopped). In other words, principal devices of the refrigeration cycle device is disposed in an engine room, and the temperature of the engine room becomes very high due to heat generated from engine devices such as an engine and an engine radiator, solar insolation during summer and the like. Consequently, the temperature of the refrigerant in the refrigeration cycle device also becomes very high, and the pressure of the refrigerant increases excessively.
In contrast, in Patent Literature 1, a vehicular air conditioning device that performs air conditioning in a vehicle compartment by using a coolant heated or cooled by the refrigeration cycle device is described. Specifically, in a condenser which constitutes part of the refrigeration cycle device, a coolant is heated by a heat exchange caused between a high-temperature refrigerant and the coolant, and the coolant is cooled by a heat exchange caused between a low-temperature refrigerant and the coolant in a chiller which constitutes part of the refrigeration cycle device.